Spring-loaded post extension for resilient support of ceiling grids during seismic events

ABSTRACT

A spring-loaded post extension for resilient support of ceiling grids during seismic events. The post extension includes a fixed cylindrical housing and a movable spring-biased assembly, axially coincident therewith. The housing is connected to the side of a fixed support post. The assembly includes a support tube extending partly within the lower end of the cylindrical housing. The bottom of the support tube is connected to a ceiling grid junction. A threaded rod has an upper portion extending above the upper end of the housing, and a lower portion extending through the housing to connect to the top of the support tube. An exterior spring fits over the upper portion of the rod, and an interior spring fits over the lower portion of the rod. Nuts on the rod provide means to tension both springs into slight compression, defining a spring-biased normal position for the support tube.

PRIORITY CLAIM

Pursuant to the provisions of 35 U.S.C. § 119(e)(1), Applicant claims the priority of U.S. Provisional Patent Application Ser. No. 60/923,931, filed Apr. 16, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of apparatus for suspending dropped ceiling grids used to support a plurality of ceiling tiles. More particularly, the invention pertains to a spring-loaded post extension which allows a resiliently supported ceiling grid to make vertical excursions during a seismic event to minimize damage and return the suspended ceiling to a normalized position.

2. Description of the Prior Art

Modern office buildings often employ a dropped ceiling grid and associated ceiling tiles, defining an air plenum between the upper side of the grid and the ceiling. This plenum is typically used to supply temperature conditioned air to the office space and to accommodate other utility services, such as lighting, electrical wires, and plumbing. The ceiling grid is suspended by a plurality of rigid support posts, extending vertically downwardly from the ceiling to a grid junction. A number of guy wires extend upwardly in diverging fashion from each grid junction to attachment points, either on the ceiling or on an adjacent wall. The guy wires prevent lateral shifts and downward vertical movement of the grid junction and the connected grid pieces. Ceiling tiles are supported by horizontal lip extensions on the grid pieces, effectively forming a dropped ceiling in the office space.

During a seismic event, forces in different directions and of varying nature are applied to the suspended ceiling grid, often with disastrous results. Earthquake forces may be abrupt excursions through a horizontal or a vertical plane, or they may be more wave-like in motion. Since the ceiling grid has a certain mass which is suspended in spaced relation from the ceiling, the ceiling and the walls will typically move first, in general coincidence with the earthquake forces. However, the motion of the ceiling grid lags that of the ceiling and walls, and develops motion overshoot and in some cases harmonic motion as the earthquake continues. As a consequence, even relatively minor seismic events can cause an inordinate amount of damage to suspended ceiling grids.

The apparatus of the present invention is designed to mitigate such damage, without major changes in the overall construction techniques for suspended ceilings which are currently employed. The apparatus taught herein may be retrofit to modify existing suspended ceilings, and may also be employed to advantage in new construction.

SUMMARY OF THE INVENTION

The apparatus herein comprises one or more spring-loaded post extensions, adapted for resilient support of a ceiling grid during a seismic event. Each post extension comprises a fixed cylindrical housing and a movable spring-biased assembly. Both the cylindrical housing and the spring-biased assembly are elongated, and axially coincident. The cylindrical housing includes flanges for screw connection to the side of a fixed support post extending vertically downwardly from the ceiling. The housing also includes attachment ears adjacent its lower end. Guy wires extend upwardly and outwardly from the attachment ears either to the ceiling or to an adjacent wall. The guy wires maintain the cylindrical housing and the support post in vertical relation, and resist lateral movement.

The spring-biased assembly includes a vertical support tube, having an upper section extending partly within the lower end of the cylindrical housing. A lower section of the support tube includes a flat or flange which is bolted to a ceiling grid junction. The assembly also includes a threaded rod, having an upper portion extending above the upper end of the cylindrical housing, and a lower portion extending through the cylindrical housing for connection to the top of the support tube.

An exterior spring fits over the upper portion of the rod, and an interior spring fits over the lower portion of the rod. Nuts on both ends of the rod provide means to tension both springs into slight compression, defining a spring-biased normal position for the support tube.

The spring-loaded post extension allows vertical excursions of the ceiling grid junction, in either upward or downward directions. Simultaneously, the post extension provides a restorative resilient axial bias, depending on the direction of the vertical excursion, to return the grid junction to its normal vertical position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, taken from a low angle, showing a suspended ceiling grid in combination with a plurality of the spring-loaded post extensions of the present invention;

FIG. 2 is a low-angle perspective view of a prior art fixed support post;

FIG. 3 is a low-angle perspective view of the spring-loaded post extension secured to a support post and a ceiling grid junction;

FIG. 4 is a perspective view, showing how the post extension is attached to a support post and to the ceiling grid junction;

FIG. 5 is an exploded perspective view of the spring-loaded post extension;

FIG. 6 is a cross-sectional view of the spring-loaded post extension in a normal position;

FIG. 7 is a view as in FIG. 6, but showing a downward excursion of the post extension; and,

FIG. 8 is a view as in FIG. 6, but showing an upward excursion of the post extension.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings, the spring-loaded post extension 11 comprises a fixed cylindrical housing 12 and a movable spring-biased assembly 13. Housing 12 preferably includes pairs of flanges 14 for screw attachment to the side of a fixed support post 16. Alternative means of attachment between the two structures may be employed, such as clamps, brackets, rods, and spot welds.

Support post 16 is identical to prior art support post 17 (see, FIG. 2), except it is slightly shorter in length. In the event of new construction, support post 16 may be manufactured to the length shown in FIG. 3. In the event of a retrofit of the assembly 13 to an existing dropped ceiling construction, prior art support post 17 may be cut off at its lower end to the appropriate length. The upper end of support post 16 is bolted to a channel bracket 18, which in turn, is affixed to the ceiling surface 19.

Support post 16 also includes a plurality of attachment ears 21, adjacent its lower end. Ears 21 may be spot welded to support post 16, preferably at 90° spaced intervals as shown in FIG. 3. In the event that a prior art support post 17 is retrofitted with extension 11, an ear collar (not shown) having four protruding ears similarly arranged, may be welded or screwed to the lower end of post 17 after it is shortened as described above. Guy wires 22 extend upwardly and outwardly from each ear 21, for attachment either to the ceiling surface 19 or to the wall surface 20. Guy wires 22 maintain both cylindrical housing 12 and the attached support post 16 in vertical relation. The guy wires also act to resist lateral movement of the housing 12 and the post 16, independent of that undergone by the ceiling and walls. In other words, under forces generated by a seismic event, the housing and the post move generally in concert with the ceiling and the walls to which they are attached in fixed relation.

The spring-biased assembly 13 includes a vertical support tube 23, having an upper section which extends partly within the lower end of cylindrical housing 12. Tube 23 also has a lower section provided with a connection flat 25. The outer diameter of support tube 23 and the inner diameter of housing 12 are such that tube 23 is able to slide freely within the confines of housing 12.

Assembly 13 also includes a threaded rod 24 having an upper portion 26 which extends above an upper end 27 of housing 12. Rod 24 also has a lower portion 28 which extends through housing 12 to connect to a top 29 of support tube 23. For that purpose, a washer 31 is welded to tube 23 to pass rod 24 and to provide a backing against which nuts 32 may be tightened.

Assembly 13 further includes an exterior spring 33 fitted over the upper portion 26 of rod 24, and an interior spring 34 fitted over the lower portion 28 of rod 24. A nut 36 and a washer 37 are provided on the upper portion 26 of rod 24. Nut 36 is adjusted along the length of upper portion 26, and nuts 32 are adjusted along the length of lower portion 28, respectively, to tension exterior spring 33 and interior spring 34 into compression against upper end 27 of housing 12. This state of compression, with both springs providing opposing bias forces, defines a spring-biased normal position for support tube 23 as shown most clearly in FIG. 6.

When the post extension 1 of the present invention is used to support a ceiling grid 38, the connection flat 25 on the lower section of support tube 23, is bolted to a ceiling grid junction 39 (see, FIG. 3). In a typical installation, a plurality of post extensions 11 are employed, each used in connection with a respective support post 16, as shown in FIG. 1. A plurality of guy wires 22 are also arranged and mounted as discussed previously, to secure the ceiling grid 38, the post extensions 11, and the support posts 16.

During a seismic event, the spring-loaded post extensions 11 allow vertical excursions of the ceiling grid junctions 39, in either upward or downward directions. For example, in FIG. 7 it is evident that the support tube 23 and the attached ceiling grid junction 39 are moving vertically downwardly with respect to the fixed cylindrical housing 12. And, in FIG. 8, it will be appreciated that support tube 23 and the attached ceiling grid junction 39, are moving vertically upwardly with respect to the fixed cylindrical housing 12.

As either of these vertical excursions occurs, the post extension 11 of the present invention provides a restorative resilient axial bias, depending on the direction of the vertical excursion, to return the grid junction to the normal position, shown in FIG. 6. Thus, by allowing controlled vertical excursions in combination with a restorative bias to a normal position, the ceiling grid is allowed to partake in some vertical movement in response to seismic forces. Owing to the spring-loaded suspension of the grid, the motion overshoot and simple harmonic motion activity encountered with the rigid prior art support post shown in FIG. 2 are diminished, and much of the damage which might have otherwise occurred to the ceiling grid is avoided. 

1. A post extension for resiliently supporting ceiling grids during seismic events, comprising: a. a fixed cylindrical housing; b. a movable spring-biased assembly, said cylindrical housing and said assembly being axially coincident, said assembly including: a support tube having an upper section extending partly within a lower end of said cylindrical housing; a threaded rod, said threaded rod having an upper portion extending above an upper end of said housing, and further having a lower portion extending through said housing to connect to a top of said support tube; an exterior spring fitting over said upper portion of said rod; an interior spring fitting over said lower portion of said rod; and, c. means to tension said exterior spring and said interior spring into compression against said upper end of said housing, defining a spring-biased normal position for said support tube.
 2. A post extension as in claim 1 including flanges along an outer wall of said cylindrical housing, for attachment to the side of a fixed support post.
 3. A post extension as in claim 1 including attachment ears adjacent a lower end of said cylindrical housing.
 4. A post extension as in claim 1 in which said means to tension said exterior and interior springs comprises bolts and washers on said upper portion and said lower portion of said threaded rod.
 5. A post extension as in claim 1 in which said support tube includes a lower section provided with ceiling grid connection means.
 6. An apparatus for resilient support of a suspended ceiling grid during a seismic event, comprising: a. a fixed support post extending vertically and downwardly from a ceiling; b. a post extension including a fixed cylindrical housing and a movable spring-biased assembly, said cylindrical housing and said spring-biased assembly being elongated and axially coincident, said cylindrical housing including flanges along an outer wall for connection to a side of said support post and further including a plurality of attachment ears on a lower end of said housing; c. opposing bias means for resiliently interconnecting said housing and said spring-biased assembly into a normal position, allowing axial excursions of said assembly with respect to said housing in either direction; and, d. a plurality of guy wires extending vertically in diverging fashion from said attachment ears to the ceiling.
 7. An apparatus as in claim 6 in which said spring-biased assembly further includes a support tube having an upper section extending partly within a lower end of said cylindrical housing.
 8. An apparatus as in claim 7 in which said support tube includes a lower section provided with ceiling grid connection means.
 9. An apparatus for resilient support of a suspended ceiling grid during a seismic event, comprising: a. a plurality of fixed support posts extending vertically and downwardly from a ceiling; b. a plurality of post extensions, each said post extension including a fixed cylindrical housing and a movable spring-biased assembly, said cylindrical housing and said spring-biased assembly being elongated and axially coincident, said cylindrical housing including flanges along an outer wall for connection to a side of a respective said support post and further including a plurality of attachment ears on a lower end of said housing; c. opposing bias means for resiliently interconnecting each said housing and each said spring-biased assembly into a normal position, allowing axial excursions of each said assembly with respect to a respective said housing in either direction; and, d. a plurality of guy wires extending vertically in diverging fashion from each of said attachment ears to the ceiling.
 10. An apparatus as in claim 9 in which each said spring-biased assembly further includes a support tube having an upper section extending partly within a lower end of a respective said cylindrical housing.
 11. An apparatus as in claim 10 in which each said support tube includes a lower section provided with ceiling grid connection means.
 12. A post extension for resiliently supporting ceiling grids during seismic events, comprising: a. an elongated fixed cylindrical housing having a side wall and a lower end, said cylindrical housing including flanges along said outer wall for connection to a support post and further including a plurality of attachment ears on said lower end; b. an elongated support tube having an upper section extending partly within said lower end of said cylindrical housing, said support tube and said cylindrical housing being axially coincident; and, c. opposing bias means for resiliently interconnecting said housing and said spring-biased assembly into a normal position, allowing axial excursions of said support tube with respect to said cylindrical housing in either direction.
 13. An apparatus as in claim 12 in which said opposing bias means comprises: a threaded rod, said threaded rod having an upper portion extending above an upper end of said housing, and further having a lower portion extending through said housing to connect to a top of said support tube; an exterior spring fitting over said upper portion of said rod; and, an interior spring fitting over said lower portion of said rod.
 14. An apparatus as in claim 13 further including bolts and washers on said upper portion and said lower portion of said threaded rod to tension said exterior spring and said interior spring into compression against said upper end of said housing.
 15. An apparatus as in claim 14 in which said support tube includes a lower section provided with ceiling grid connection means.
 16. An apparatus as in claim 15 further including a fixed support post extending vertically and downwardly from a ceiling, said flanges on said cylindrical housing being connected to said support post.
 17. An apparatus as in claim 12 further including a plurality of guy wires extending vertically in diverging fashion from each of said attachment ears to a ceiling. 